JPS59143028A - Cooler for metallic strip in continuous heat treating furnace - Google Patents

Abstract

PURPOSE:To cool uniformly a metallic strip in its horizontal direction in the stage of cooling the metallic strip with a water-cooled roll in a continuous annealing furnace by forming the water-cooled cooling roll by shrinkage fit of a sleeve having cooling water paths onto a roll shaft. CONSTITUTION:The construction of a water-cooled roll to be used in the stage of cooling a metallic strip 1 by bringing the strip into contact with said roll is constructed by fixing a sleeve 11 by shrinkage fit to a roll shaft 12 having a supplying port 13 and discharging port 14 for cooling water and providing cooling water paths 15 on either the sleeve or the shaft 12. The sleeve 11 in the part that contacts the strip 1 of a high temp. expands as the temp. in said part rises in the stage of cooling the strip 1 but the tensile stress T owing to the shrinkage fit decreases in the range of the shrinkage fitting stress and therefore the quantity at which the above-described thermal expansion appears as a heat crown of the roll is considerably offset. The strip 1 is uniformly cooled without the uneven contact between the strip to be cooled and the sleeve 11 by the said effect.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a method for cooling a heated metal strip in a continuous heat treatment furnace by bringing it into contact with a cooled roll, so that the strip is cooled uniformly in the width direction and at a predetermined cooling rate. This invention relates to a cooling device that achieves cooling.

[Prior art]

In recent years, a technology (continuous annealing technology) has been developed to produce cooled steel sheets with excellent drawability and workability using a continuous heat treatment furnace instead of batch annealing, resulting in higher productivity and lower costs than conventional batch annealing. Therefore, there is a tendency for continuous annealing equipment to be more widely adopted in the future.

A typical thermal cycle in this continuous annealing equipment is shown using FIGS. 1 and 2 using a copper strip as an example.

FIG. 1 shows a gas jet cooling method in which thorn cooling is performed by blowing cold gas directly onto a heated copper strip. FIG. 2 shows a water cooling method in which the heated steel strip 6 is cooled by water spraying and immersion. These conventional methods have the following drawbacks.

(1) In the gas jet cooling method, it is difficult to obtain a high cooling rate (100° C./sec).

(2) In the water cooling method, although the cooling rate is fast, it is not possible to control the end point temperature, and since the copper strip is cooled to room temperature, it is necessary to reheat the copper strip to the predetermined temperature required for overaging treatment. Moreover, since the surface of the steel plate is oxidized, treatments such as pickling are required, which increases equipment costs.

Operating costs are high.

One way to overcome these drawbacks of conventional methods is to
A roll cooling method has been proposed, in which a heated metal strip is rotated by applying a predetermined tension to a rotating roll that is continuously cooled by a refrigerant. With the existing roll cooling method, it is difficult to uniformly cool the metal strip in the width direction due to the following factors.

■ For rolls used for roll cooling, the roll temperature at the part where the metal strip contacts the long side of the roll body rises higher than the roll temperature at the non-contact part, so a heat crown is formed on the roll, and both ends of the metal strip are cooled. Contact with the rolls becomes difficult and the ends of the metal strip remain uncooled. When temperature non-uniformity occurs in the width direction of the metal string due to the above phenomenon, the cooled part causes thermal contraction, and the tension distribution of the metal strip becomes uneven, with high tension in the cooled part and low tension in the uncooled part. It becomes tension.

The cooled parts, that is, the parts with high tension, come into closer contact with the cooling roll, and the uncooled parts, that is, the parts with low tension, have even more difficulty in contact with the cooling roll, and the temperature in the width direction of the metal tube increases. The non-uniformity is further amplified.

■ To deal with the above problems, (a) a cooling medium other than water that can be used at high temperatures is used as the cooling medium for the cooling roll;
A method of reducing temperature non-uniformity in the width direction by suppressing the temperature difference between the pump and the cooling roll within a certain range (Japanese Patent Laid-Open No. 57-23036) A method of equalizing the temperature distribution in the lengthwise direction of the roll by dividing the inside of the roll in the lengthwise direction of the roll and controlling the refrigerant temperature and refrigerant flow rate in each refrigerant passage (Japanese Patent Application Laid-Open No. 18315-1983), etc. However, in the method (a), the cooling efficiency (cooling rate of the metal strip) is significantly lower than when water is used as a refrigerant for cooling the rolls, and the effect of reducing the heat crown of the rolls is not sufficient. . Also, the above (r+
), it is difficult to arbitrarily reduce the amount of refrigerant in the width direction in order to prevent bumping of the refrigerant within the roll, and therefore it is difficult to suppress the heat crown of the roll to a sufficiently small size. Have difficulty. Furthermore, both of the above two means require a complicated structure of the cooling roll and a large-scale control device, making them uneconomical.

[Purpose of the invention]

The present invention relates to an apparatus for cooling a metal strip heated in a continuous heat treatment furnace by applying a predetermined tension to a continuously cooled roll, thereby cooling the strip. This is an attempt to solve the problems of That is, the object is to easily and economically suppress the heat crown of the cooling roll, which is a major cause of uneven cooling of the strip in the width direction.

[Structure and operation of the invention]

In order to achieve the above object, the present invention provides equipment for cooling a metal strip in a roll in a continuous heat treatment furnace, specifically, a roll for cooling a metal strip continuously with a cooling medium.
Nut l) The configuration described in F is adopted in a roll cooling device that cools while contacting with a predetermined wrapping angle (or wrapping area) determined by conditions such as the thickness of the tube, processing speed, and refrigerant temperature. It is characterized by

That is, the present invention provides a refrigerant circulation passage on at least one of the inner surface of the shaft sheath (sleeve) and the outer surface of the roll shaft. It is characterized in that the shaft sheath is shrink-fitted and fixed to the t)'lJl diary journal shaft held in the core. This creates a circumferential tensile stress in the shaft sheath and cools the hot metal string while circulating the refrigerant through the refrigerant passage;
The thermal expansion that occurs at that time is significantly reduced by the shrink fit stress.

Next, the necessity of suppressing the heat crown of the cooling roll and the gist of the present invention will be explained using drawings and mathematical formulas.

FIG. 3 shows an example of roll arrangement in the cooling section of a continuous heat treatment furnace. In the figure, 1 is a metal strip to be cooled, 2
, 3, 9, and 10 are priddle rolls for applying a predetermined tension to the strip to be cooled; 4, 8 are deflector rolls; and 5, 6.7 are cooling rolls; The refrigerant is continuously supplied, circulates through a refrigerant passage provided inside the roll, and is cooled by being discharged from the roll shaft to the outside of the roll.

The number of cooling rolls is determined by the continuous heat treatment/processing furnace capacity, etc. In the roll cooling of metal strut l)
The metal stamp temperature To at the exit of the cooling roll is as follows (1
) can be expressed by the formula.

Here, K is the heat transmission coefficient between the metal strip and the refrigerant, and can be expressed by the following equation (2).

In the above equations (1) and (2), To = Strip exit temperature (C°C) Ti: ” Inlet temperature (°C) Ts:
// Average temperature (℃) Tw Two refrigerant temperatures ('
C) θ Winding angle of Nistrip on cooling roll (radian) R: Cooling roll radius (7n) h Nistrip thickness (m) ■ : Strip width (m/m1n) k, Heat between Nistrip and cooling roll Transmission rate (kcal
/m2hr℃) k2: Heat transfer coefficient between cooling roll and refrigerant (kcal
, /TrL2hr ℃)λ Thermal conductivity of the material of the second cooling roll (kcal/mhr℃) d: Thickness between the cooling roll strip and the refrigerant (m) In the above equations (1) and (2), Ti・θ ,R,Tw,
There is little variation in the values of h and V in the width direction of the metal strut, and the influence on the strump exit temperature TO can be ignored. Therefore, it can be seen that making the heat transfer coefficient uniform in the width direction is the key to making the temperature distribution in the width direction uniform.

The heat transfer coefficient between the strip and the cooling roll, 1, is determined by the roughness of the strip surface and the roll surface and the contact surface pressure between the strip and the roll surface, and can be expressed by the following equation (3).

k,=Ap'・
...(3) Here, A is a constant due to the roughness of the strip surface and the roll surface.P is the contact surface pressure between the strip and the roll (kg/dimension n: constant. From the inventor's experimental values, equation (3) The constants are considered to be as follows in normal cooling of metal strips.

30000p05 in k1 Normally, the strip roughness and roll roughness can be considered to be the same in the width direction of the strip, so 1 for the heat transfer coefficient between the strip and the roll in the width direction of the strip is the contact surface between the strip and the roll. It can be said that it is determined by pressure. The heat crown of the cooling roll is the largest factor that makes the contact surface pressure between the string and the roll non-uniform in the width direction.In order to suppress this heat crown, the present invention This purpose is achieved by shrink-fitting the sleeve to the roll shaft.

〔Example〕

Embodiments of the present invention will be described below in detail with reference to the drawings. Figures 4 and 5 do not show the outline of the roll structure according to the present invention. As shown in Figures 4 and 5, the cooling roll The sleeve 11 is fixed to the roll shaft 12 by a shrink fit.The refrigerant is supplied from an independent annular groove refrigerant supply port 13 provided in the axial center of the roll shaft 12, and is provided in a spiral shape on the inner surface of the sleeve 11. The sleeve 11 and the roll shaft 12 are cooled through the refrigerant passage 5, and are discharged from the refrigerant outlet 14 at the other end of the shaft.The refrigerant passage 15 is not limited to a spiral shape, but is formed by a plurality of independent annular grooves. As shown in FIG. 5, the sleeve 11 is subjected to a tensile stress T in the circumferential direction due to the shrink fit, and the roll shaft 12 is subjected to a compressive stress C due to the shrink fit.
is working.

As shown in Fig. 4, during roll cooling, the temperature of the part of the sleeve that is in contact with the strip 1 increases;
The temperature of the roll shaft 12 is maintained at approximately the same temperature as the refrigerant. For this reason, thermal expansion occurs in the part of the sleeve 11 that contacts the pimple 1 and increases in temperature, but within the shrink fit stress range, the tensile stress due to the shrink fit decreases, causing the thermal expansion. The amount of heat that appears as a heat crown is greatly reduced. Metals cooled by this effect)
Non-uniform contact between the knob 1 and the snub 11 is greatly suppressed, and non-uniform string cooling is also greatly improved.

Other embodiments of the present invention are shown in FIGS. 6, 7, and 8 (
Indicated by FIG. 6 shows an embodiment in which a refrigerant circulation passage 15 is provided on the outer surface on the roll shaft side. FIG. 7 shows an embodiment in which a refrigerant circulation passage 15 is formed by providing grooves in both the sleeve 11 and the roll shaft 120 and aligning the positions of both grooves. FIG. 8 shows an embodiment in which a refrigerant supply port 13 and a refrigerant discharge port 14 are provided at both ends of the roll shaft. In this case, the temperature difference between both ends of the cooling roll is smaller than when the refrigerant is supplied from one end of the roll shaft and discharged from the other end, as shown in FIG.

In the embodiments of the present invention, the cross sections of the refrigerant passages are all square or rectangular, but they may also be circular or elliptical.

In the present invention, it is preferable that the shrink fit between the sleeve and the roll shaft is at least a value that does not reduce the shrink fit to zero within that temperature range, taking into account the anticipated temperature rise of the sleeve. If the shrinkage fit is restricted due to the strength of the material, a sufficient heat crown suppression effect can be expected within the allowable shrinkage fit. For example, in Figure 5, R
,= 650 jobs, R2=730mm-R3=750mm
In this case, by setting the shrinkage fit to about 3 mm in diameter, it is possible to significantly suppress heat crown when the sleeve temperature rises to about 200°C. , FIG. 9 shows an example of the heat crown suppressing effect according to the present invention. Furthermore, FIG. 10 shows an example of the strip temperature distribution on the exit side of the cooling roll when the present invention is implemented and when the invention is not implemented, for a strip width of 1000 mm. As shown in FIG. 10, when the present invention is implemented, the temperature distribution on the exit side of the cooling roll is greatly improved, and the effects of the present invention are obvious.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to effectively suppress the heat crown of the cooling roll, and it is possible to effectively suppress the heat crown of the cooling roll.
Sufficient uniform cooling in the width direction of the tube can be achieved. Therefore, according to the present invention, it has become possible to employ a roll cooling device, which was previously limited to use due to the drawback that it is difficult to control the temperature unevenness in the width direction of the metal strip after cooling. Further, by realizing roll cooling that can economically achieve uniform temperature distribution in the width direction of the sheet, the following effects can be obtained.

(1) The cooling rate of the metal strip can be significantly increased compared to gas jet cooling means (gas jet cooling: 1
0-b 100°C/sec). Therefore, it can be expected that the mechanical properties of the finished product in a continuous heat treatment furnace will be similar.

(2) Furthermore, since the cooling rate described above can be achieved uniformly in the width direction of the plate, unevenness in quality of the finished product can be reduced.

(3) Non-oxidizing cooling eliminates the need for post-treatments such as pickling, making it economical.

[Brief explanation of the drawing]

FIG. 1 shows a thermal cycle in continuous annealing of cold-rolled steel sheets by gas jet cooling. FIG. 2 shows the thermal cycle in continuous annealing of cold rolled steel sheets by water cooling. Third
The figure shows an example of equipment layout for a roll cooling device. FIG. 4 shows a schematic cross-section of the structure of a cooling roll according to the present invention, taken along the roll axis. FIG. 5 schematically shows the structure of a cooling roll according to the present invention in a cross section perpendicular to the roll axis. Figures 6, 7, and 8 show other embodiments of the present invention. Figure 6 shows an example in which a refrigerant circulation passage is provided on the roll shaft side, and Figure 7 shows an example in which a refrigerant circulation passage is provided on the roll shaft side. An example in which grooves forming passages for refrigerant circulation are provided on both roll shafts, and FIG. 8 shows an example in which both a refrigerant supply port and a refrigerant discharge port are provided at each end of the roll shaft. . FIG. 9 shows a comparison of the amount of heat crown when the present invention is implemented and when the present invention is not implemented. FIG. 10 shows a comparison of the temperature distribution of the metal strip on the exit side of the cooling roll when the present invention is implemented and when the invention is not implemented. DESCRIPTION OF SYMBOLS 1... Metal strip, 2, 3... Entrance side tension pry roll, 4... Deflector roll, 5, 6.7... Cooling roll, 8... Deflector roll, 9.10... Exit tension pry roll, 11...sleeve, 12...° roll axis,
13... Refrigerant supply port, 14... Refrigerant discharge port, 1
5... Refrigerant passage patent applicant representative patent attorney Tomoyuki Yabuki (and one other person) Figure 1 Figure 2 (Mizumo 5p) Figure 3 Figure 4 Figure 5 Figure 6 Figure 8 5 to 11gu・＼(+$)

Claims (1)

[Claims] A roll cooling device that cools a metal string in a continuous heat treatment furnace while being brought into contact with a roll that is continuously cooled by a refrigerant, the refrigerant circulating on at least one of the inner surface of the shaft sheath and the outer surface of the roll shaft. Metal in a continuous heat treatment furnace, characterized in that the shaft sheath is shrink-fitted and fixed to the roll shaft, which has a passageway and has one or more refrigerant supply ports and one or more refrigerant discharge ports in the shaft core. Strip cooling device.